TABLE 1.

P. otitidis strains investigated in this work, MBL activity measured in crude extracts, and MICs of various β-lactams

Source of strain or MIC parametera	Strain	MBL productionb	MIC (μg/ml) of β-lactamc:
			IMP	MEM	PIP	AZT	CTX	CAZ
CU	MCC04446	46.0	0.75	3	1.5	6	6	6
CU	MCC04511	28.7	>32	>32	4	6	4	2
CU	MCC04517	37.8	3	6	3	4	2	6
CSOM	MCC09159	44.7	2	−12	0.75	2	1.5	4
AOE	MCC10330T	42.3	3	3	4	4	2	6
AOE	MCC10429	58.1	2	2	6	4	6	8
AOE	MCC10744	66.7	1	2	4	6	4	3
AOE	MCC11140	42.4	1.5	1	4	6	3	6
AOE	MCC11061	28.5	1	2	4	8	3	4
AOE	MCC11338	41.1	1	3	1.5	2	2	4
AOE	MCC11683	30.3	1	1.5	0.75	6	4	4
AOE	MCC12065	38.8	0.5	4	1.5	6	2	4
AOE	MCC12178	36.2	1.5	2	4	8	3	3
AOM	MCC40150	17.9	1	2	1.5	3	1.5	3
AOM	MCC40159	16.6	0.75	6	4	8	4	3
AOM	MCC51196	15.1	0.75	0.25	1	6	3	3
AOMT	MCC61379	97.2	2	16	3	6	4	4
AOMT	MCC61485	16.1	2	2	2	6	2	3
AOMT	MCC61433	31.5	2	24	3	4	4	4
CSOM	YMC-Po/06	81.7	>32	>32	2	4	3	4
MIC range			0.50->32	0.25->32	0.75-6	2-8	1.5-6	2-8
MIC50			1.5	3	3	6	3	4
MIC90			3	24	4	8	4	6

^aCU, corneal ulcer; CSOM, chronic suppurative otitis media; AOE, acute otitis externa; AOM, acute otitis media; AOMT, otitis media with otorrhoea drainage through tympanostomy tube.

^bMBL production is shown in nanomoles of imipenem hydrolyzed per minute per milligram of protein. Data are the mean values of measurements for three replicate samples (the standard deviation was always <10%); in all cases, the activity was inhibited by at least 80% in the presence of EDTA. Carbapenemase activity measured with the negative control (P. aeruginosa ATCC 27853) yielded a value of <10 nmol of imipenem hydrolyzed/min/mg of protein.

^cThe MICs were determined by Etest. IMP, imipenem; MEM, meropenem; PIP, piperacillin; AZT, aztreonam; CTX, cefotaxime; CAZ, ceftazidime.